1. Field of the Invention
The present invention is in the field of effervescent granulates containing an edible organic acid coated with a calcium carbonate-containing layer, the two being bonded at the interface by means of a reaction product between the acid and the carbonate.
2. Description of the Prior Art
Effervescent tablets are usually based on the reaction of an organic acid such as citric acid, tartaric acid, and a substance which liberates CO.sub.2, such as sodium bicarbonate, sodium carbonate, potassium bicarbonate or potassium carbonate. There have been frequent criticisms that such systems have an excessively high proportion of sodium ions and it would be desirable to provide an effervescent system in which fewer or possibly no sodium ions were contained. The utilization of potassium bicarbonate and potassium carbonate alone fails to meet the need because, first, the potassium compounds give the substance an unpleasant soapy taste, and second, the moisture sensitivity due to the introduction of potassium salts leads to great technical problems.
It would be desirable to employ carbon dioxide liberating agents such as calcium carbonate and magnesium carbonate. Calcium carbonate would be preferred but it cannot be employed without difficulty because it reacts extremely slowly with an organic acid and therefore effervescent systems containing calcium carbonate require far too long to dissolve.
European OS No. 0 076 340 discloses an effervescent granulate as well as a method wherein, using citric acid as the organic acid, the acid crystals are provided with a single-layer coating which contains calcium carbonate. Such effervescent granulates or effervescent mixtures have definitely proven themselves whether used as instant mixes for producing effervescent beverages or employed in the manufacture of effervescent tablets. Still, it is desirable to further increase the calcium content of such effervescent granulates. This has proven difficult because calcium carbonate reacts extremely slowly with organic acids and effervescent systems which rely solely on such sources of calcium carbonate take a long time to dissolve.
What is especially desirable is an improvement of the known effervescent granulate as well as a method for the manufacture thereof to provide further improvement in the storage properties, and an increase in the calcium concentration together with simultaneous enhancement of the solubility in water.